As background, submucosa tissues have been suggested and used as tissue graft materials. For example, U.S. Pat. No. 2,127,903 to Bowen describes various tubes for surgical purposes which may be constructed of the submucosa layer of animal intestinal tissue. Bowen teaches constructing the tubes using a multiplicity of tissue ribbons or threads which are wound over a tubular form and dried.
U.S. Pat. No. 3,562,820 to Braun describes the use of submucosa or serosa tissues to form prosthesis devices. In one embodiment, Braun describes preparing a tubular prosthesis by drawing submucosa over a tube and drying the tissue. Braun teaches that this procedure may be repeated until the desired wall thickness is obtained.
U.S. Pat. No. 4,956,178 to Badylak et al. teaches tissue graft compositions comprising the tunica submucosa of a segment of small intestine of a warm-blooded invertebrate, wherein the tunica submucosa is delaminated from the tunica muscular and at least the lumenal portion of the tunica mucosa. Badylak et al. teaches creating tubular constructs by manipulating a sheet of the tissue graft composition to define a cylinder and suturing or otherwise securing the tissue longitudinally.
U.S. Pat. No. 6,358,284 to Fearnot et al. describes the preparation of a tubular graft from a purified submucosa sheet, wherein a first and second opposite edge of the sheet are overlapped, and wherein layers in the overlapped region are fixed to another. The Fearnot et al. patent also discloses the potential of having a second layer of submucosa tissue overlying the first layer.
WO 01/10355 published Feb. 15, 2001 describes tubular grafts of biomaterial, such as submucosa, having lumen walls which present no seam edge traversing the entire length of the lumen, for example, wherein the lumen walls present a discontinuous seam. As described, such a device can be made using a biomaterial sheet having a plurality of extensions and a plurality of corresponding apertures. The sheet can be configured as a cylinder and the extensions extended through the apertures in the formation of the tubular medical device.
WO 01/82836 A2 published Nov. 8, 2001 describes an endovascular stent graft with a stent frame having a plurality of stents connected together with a monofilament line. A covering of collagen having an extracellular matrix (ECM), such as small intestine submucosa (SIS) is disposed through the inside and over the outside of the stent frame. The covering is affixed to the stent frame such as by being sutured onto the stent frame at the ends of the stent frame and also at the connections of the stent bodies, such as at eyelets.
U.S. Pat. No. 5,693,085 to Buirge et al. describes a stent with collagen in which the collagen is applied to the outside surface of a vascular stent.
U.S. Pat. No. 5,916,264 to Von Oepen et al. describes a stent graft having two coaxially arranged, radially expanded stents and a flexible, stretchable material layer arranged between the stents. Both stents are directly connected with one another in their end regions and the material layer is formed as a fabric band wound around an inner stent. The material layer is composed of a foil or a fabric from a body compatible material or of a biological fabric. The biological material can include an autologous or homologous vein or artery.
endoluminal exclusion of an abdominal aortic aneurysm (AAA) by Transluminal implantation of stent grafts has in selected cases become an attractive alternative to open surgical aneurysmal repair. Endoluminal exclusion has been done on an elective basis after detailed preoperative visualization and measurements have been made of the aneurysmal and adjacent arterial anatomy. Stent graft systems for both elective and emergency AAA exclusions have been typically constructed with conventional surgical synthetic materials such as DACRON or polytetrafluoroethylene (PTFE) supported by typically metallic expandable stents.
Conventionally, stent grafts placed within the vascular system include one or more stents of affixed graft material including biological materials in addition to the conventional synthetic materials. As previously suggested, these biological materials can include tissue which is affixed to one or more longitudinally positioned stents using, for example, sutures which are affixed to folded over tissue at the ends of the stents and similarly along the lengths of the stents. As suggested by the Von Oepen patent, stents can be used to sandwich a stretchable material layer arranged longitudinally between the two stents. However, the stents are directly connected with one another at their end regions making the end regions significantly more rigid thereat than the intermediate portion therebetween. Abrupt transitions between the stented and unstented portions can cause significant trauma and undesirable intimal hyperplasia with consequent narrowing of the vessel. This consequence is typically referred to as “edge effect.” Attachment sutures or other attachment configurations allow for a leakage of blood through the covering material, thus producing undesirable and/or life-threatening endoleaks. Furthermore, simply covering a stent with a layer of tissue without any attachment thereto allows for the tissue material to be pulled back or everted over itself when a delivery catheter is pulled back over the stent graft at the implantation site. This eversion creates a significant problem in that the aneurysm is no longer excluded and in that the stent graft with its everted tissue material presents a significant problem in its removal.